Redis::exists should no longer use Boolify

[scottyschup]

In the Redis documentation for exists, as of Redis 3.0.3 exists may take multiple key names and returns a count of the number of keys that exist.

Using the redis-rb gem v3.3.3, the result of Redis::exists with an array of keys returns true if and only if just one of the keys exist. false is returned if none of the keys exist or if multiple keys do because Boolify looks for a non-nil value equal to 1.

To reproduce:

r = Redis.new
r.mset 'test1', 1, 'test2', 2
r.exists ['test1', 'nonexistant']
#=> true
r.exists ['test1', 'test2']
#=> false

So either Boolify could be adjusted to look for values >= 1, or (what makes more sense to me) Boolify should not be used in this function so that the return value is the count of the number of keys found as is described in the Redis docs.

[kumekay]

I've created a new pull request #736 to fix this issue.
It differs from #728 that it doesn't change return type of exists method. It always returns boolean:
true if all passed keys exist in database, and false if at least one is missing.

[kumekay]

If there is a real demand for number of existed keys, it can be implemented as separate method, exists_count, for example

[vgmoose]

Any update on the status of this? It looks like there are three in-progress PRs for providing functionality to accept multiple keys:

#728 by @ybinzu - uses exists, returns the count if multiple keys are provided, nil if 0 are found
#736 by @kumekay - uses exists, returns true if all provided keys exist, false if one doesn't
#741 by @ericproulx - adds mexists, returns the count of how many provided keys exist (and never nil)

Thanks to all involved and sorry for any unwanted pings

[micahbf]

Just ran into this issue as well.
Can I do anything to move this forward?

[scottyschup]

Because this issue was not resolved by the time I needed it to be, I just ended up writing a helper method in my RedisClient class to use in place of Redis#exists. It was something like:

class RedisClient
...
  @client = Redis.new
...
  def exists(keys)
    res = keys.inject(0) { |key, count| count +=1 if @client.exists(key) }
    res == 0 ? nil : res
  end
end

[byroot]

Fixed in 3257527

[simonrussell]

@byroot This resolution seems okay, but probably changing the return type should be a major version bump (5.0.0) as this is a breaking change (I'm referrering to the warning issued when you call exists) -- a lot of gems relying on this client might not (should not) be restricting the minor versions.

[simonrussell]

Also this causes gems like Sidekiq to write a lot of junk to the console -- if there was a way to turn off the message that would be good.